<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style>
 li{list-style:none;}
  #fixed_ul ul{float:left;padding:0;}
  #u1>li{ position: absolute;}
  #u1{position: relative;} 
  #u1>li:first-child{top:-30px;right:0px;}
  #u1>li:nth-child(2){top:30px;right:0px;}
  #u1>li:last-child{top:130px;right:0px;}
  #fixed_ul{position:fixed;right:0;top:50%}   
  #u2{margin-left:10px;}
  </style>
</head>
<body>
<div id="fixed_ul">
    <ul  id="u1">
        <li style="display:none"><img src="./img/pop_app.png" alt="#"></li>
        <li style="display:none"><img src="./img/pop_wechat.png" alt="#"></li>
        <li style="display:none"><img src="./img/phone.png" alt="#"></li>
    </ul>
    <ul id="u2">
        <li><img src="./img/app.png" alt="#"></li>
        <li><img src="./img/wechat.png" alt="#"></li>
        <li><img src="./img/Customer_service.png" alt="#"></li>
    </ul>
</div>
<script>
    var fixeds=document.getElementById("u2").children;
    var li_1=fixeds[0];
    var li_2=fixeds[1];
    var li_3=fixeds[2];
    li_1.onmouseover=function(){
      this.parentNode.previousElementSibling.children[0].style.display="block";
    };
    li_1.onmouseout=function(){
      this.parentNode.previousElementSibling.children[0].style.display="none";
    }
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      this.parentNode.previousElementSibling.children[1].style.display="block";
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    }
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    };
    li_3.onmouseout=function(){
      this.parentNode.previousElementSibling.children[2].style.display="none";
    }
</script>    
</body>
</html>